Patent Application
20090197165
The present invention relates to alkaline batteries, and in particular, to an alkaline battery that dispenses with the reinforcing washer used in its sealing portion. The alkaline battery has its battery volume increased by the amount corresponding to the volume of the washer and thus achieves improved discharge performance.
Alkaline batteries having a construction as represented by an alkaline battery 21 in
Fitted to the opening of the battery can 22 is a gasket 27 that is placed against the open end of the separator 25 and includes an inner cylindrical portion 27a, an outer cylindrical portion 27b, and a linking portion 27c that connects the inner cylindrical portion 27a to the outer cylindrical portion 27b. The linking portion 27c of the gasket 27 is formed by a short skirt 27e that extends downward from a lower stepped portion 27d of the outer cylindrical portion 27b, forming a slightly sloped conical cylinder, and an annular disc 27f that extends radially inward and slightly upward from the lower end of the skirt 27e. Arranged between the inner periphery of the annular disc 27f and the outer periphery of the inner cylindrical portion 27a is a thin portion 28 that serves as an explosion-proof valve. A reinforcing washer 29 is arranged on the gasket 27 between the lower stepped portion 27d of the outer cylindrical portion 27b and an upper outer stepped portion 27g of the inner cylindrical portion 27a. A negative electrode collector 30 is placed through the inner cylindrical portion 27a of the gasket 27 and through the gel-like negative electrode 26. The negative electrode collector 30 includes a head 30a to which a negative electrode terminal plate 31 is secured. The outer periphery of the negative electrode terminal plate 31 is in contact with the outer periphery of the reinforcing washer 29.
A groove 32 is formed at a certain distance from the open end of the battery can 22 to support the outer periphery of the gasket 27. The open end of the battery can 22 and the upper end of the outer cylindrical portion 27b of the gasket 27 are crimped radially inward, forming a crimped portion 33. The crimped portion 33 axially compresses the upper end of the outer cylindrical portion 27b of the gasket 27, so that the gasket 27 seals the opening of the battery can 22 and secures the negative electrode terminal plate 31. The outer periphery of the battery can 22 is covered by a thermal contractive resin tube 34.
Another type of alkaline batteries includes a battery can with an enlarged opening. A seal assembly, consisting of a gasket and a terminal plate arranged within an outer cylindrical portion of the gasket, is fitted to the enlarged opening of the battery can. The gasket includes an inner cylindrical portion, the outer cylindrical portion, a linking portion, and a thin portion arranged on the outside of the inner cylindrical portion to serve as an explosion-proof valve. To seal the battery can, the edge of the opening of the battery can is crimped inward while the opening is being compressed radially. A buffering member for absorbing the compressive deformation is arranged on the inside of the outer cylindrical portion of the gasket. The buffering member serves to prevent the operation pressure of the explosion-proof valve from being affected by the stress caused to the thin portion by the compressive force that acts during radial crimping of the battery can (See, for example, Patent Document 2).
Patent Document 1: Japanese Patent Application Laid-Open No. 2000-3696
Patent Document 2: Japanese Patent Application Laid-Open No. 11-86810
However, since the alkaline batteries described in Patent Document 1 and having a construction shown in
One possibility, therefore, is to construct a sealing portion without the reinforcing washer.
The sealing portion described in Patent Document 2 is constructed without using a metal ring (reinforcing washer). Instead, this construction includes on the inside of the outer cylindrical portion a buffering portion that has a V-shaped notch so that it can absorb the compressive deformation. This buffering member serves to keep the thin portion from being exposed to the stress caused by the compressive force that acts during radial crimping of the battery can. However, this type of alkaline battery is sealed in an essentially different way from the alkaline battery of
In view of the above-described conventional problems, it is an object of the present invention to provide an alkaline battery that not only achieves improved discharge performance by employing a sealing portion with a decreased axial dimension, but also retains its safety and leakage-proof performance.
To achieve the foregoing object, an alkaline battery of the present invention includes:
a battery can encasing a positive mixture, a separator, and a gel-like negative electrode; and
a sealing assembly for fitting to an opening of the battery can, the sealing assembly including:
Since this construction does not use the reinforcing washer, the axial dimension of the sealing portion can be decreased. As a result, the discharge performance of the battery can be improved. When the end of the outer cylindrical portion of the gasket is bent inward on the sealing process of the battery, the part is axially compressed and deformed, causing distortion and stress in the outer cylindrical portion. The distortion and stress are then transmitted to the linking portion. In this construction, however, the annular disc of the linking portion, which is uniform in thickness and has a two-step profile because of the bent portion formed at its middle portion as viewed along the radial direction, effectively absorbs the distortion and stress as it deforms at the bent portion. This makes the thin portion less susceptible to significant stress and thus, to cracks, on the sealing process. As a result, the leakage-proof performance of the battery can be ensured and the operation pressure of the explosion-proof valve can be stabilized, ensuring the safety and leakage-proof performance of the battery.
With regard to the direction of the slope of the annular disc and the direction of the bending of the bent portion, the angle A1 between the outer periphery of the inner cylindrical portion of the gasket and the portion of the annular disc inside the bent portion may be 90 degrees or less and may be greater than the angle A2 between the outer periphery of the inner cylindrical portion and the portion of the annular disc outside the bent portion. In this manner, the annular disc is recessed where it contacts the open end of the separator. This is advantageous since the splitting of the gel-like negative electrode is effectively prevented.
The difference between A1 and A2 (i.e., A1−A2) may be set in the range of 11 to 22 degrees. This is desirable since is the above-described advantageous effects can be achieved in a reliable and stable manner.
The bent portion of the annular disc may be formed as an angular inflexion point. In this manner, the bent portion becomes more susceptible to stress and the annular disc is more likely to deform. As a result, the distortion and stress transmitted from the outer cylindrical portion to the annular disc on the sealing process are more effectively absorbed. Moreover, the leakage-proof performance of the battery can be even more improved and the operation pressure of the explosion-proof valve can be even more stabilized. The angular inflexion point preferably has a radius of curvature of 0.2 mm or less.
An alkaline battery in one embodiment of the present invention will now be described with reference to
In
A groove 12 is formed at a certain distance from the open end of the battery can 2 to support the outer periphery of the seal assembly 11, or the lower end of the outer cylindrical portion 7b of the gasket 7. In this state, the open end of the battery can 2 and the upper end of the outer cylindrical portion 7b of the gasket 7 are crimped radially inward, forming a crimped portion 13. The crimped portion 13 axially compresses the upper end of the outer cylindrical portion 7b of the gasket 7, so that the seal assembly 11 including the gasket 7 and the negative electrode terminal plate 10 seals the opening of the battery can 2 and secures the negative electrode terminal plate 10. The outer periphery of the battery can 2 is covered by a thermal contractive resin tube 14.
In the alkaline battery 1 having the above-described construction, the linking portion 7c of the gasket 7 is formed by a short skirt 7e that extends downward from a stepped portion 7d at the lower inner periphery of the outer cylindrical portion 7b, forming a slightly sloped conical cylinder, and an annular disc 7f that extends radially inward and slightly upward from the lower end of the skirt 7e, as detailed in
When the end of the outer cylindrical portion 7b of the gasket 7 is bent inward on the sealing process of the battery, the part is axially compressed and deformed, causing distortion and stress in the outer cylindrical portion 7b. The distortion and stress are then transmitted to the linking portion 7b, pulling the skirt 7e radially outward with a significant force. In this construction, however, the annular disc 7f of the linking portion 7c, which is uniform in thickness and has a two-step profile because of the bent portion 7g formed at its middle portion as viewed along the radial direction, effectively absorbs the distortion and stress as it deforms at the bent portion 7g. This keeps the thin portion 8 from being exposed to significant stress during the sealing process. As a result, the leakage-proof performance of the battery can be ensured and the operation pressure of the explosion-proof valve can be stabilized, ensuring the safety and leakage-proof performance of the battery. Furthermore, eliminating the reinforcing washer from the seal assembly 11 makes it possible to design the sealing portion with a decreased axial dimension. As a result, the effective volume of the battery can 2 can be increased and, thus, the discharge performance of the battery can be improved.
With regard to the direction of the slope of the annular disc 7f and the direction of the bending of the bent portion 7g, the angle A1 between the outer periphery of the inner cylindrical portion 7a and the portion of the annular disc 7f inside the bent portion 7g may be an obtuse angle, or the angle A2 between the outer periphery of the inner cylindrical portion 7a and the portion of the annular disc 7f outside the bent portion 7g may be larger than A1. However, when A1 is smaller or equal to 90 degrees and A2 is smaller than A1, the annular disc 7f is recessed where it contacts the open end of the separator 5. This is advantageous since the splitting of the gel-like negative electrode 6 is effectively prevented. This advantageous effect becomes even more significant when the difference between A1 and A2 (i.e., A1−A2) is set in the range of 11 to 22 degrees.
More advantageously, the bent portion 7g of the annular disc 7f on the interior of the battery can may be formed as an angular inflexion point with a radius of curvature (R) of 0.2 mm or less. The bent portion 7g formed as an angular inflexion point is more susceptible to stress and, thus, more likely to deform, so that the distortion and stress transmitted from the outer cylindrical portion 7b to the annular disc 7f on the sealing process are more effectively absorbed. As a result, the leakage-proof performance of the battery can be even more improved and the operation pressure of the explosion-proof valve can be even more stabilized.
Examples of the present invention will now be described in comparison with conventional examples as Comparative Examples.
As shown in
a conventional alkaline battery as shown in
an alkaline battery as shown in
an alkaline battery 1 as shown in
an alkaline battery 1 as shown in
an alkaline battery 1 as shown in
an alkaline battery 1 as shown in
an alkaline battery having the same construction as Example 1, except that the bent portion has an angular shape as shown in
an alkaline battery having the same construction as Example 2, except that the bent portion has an angular shape as shown in
an alkaline battery having the same construction as Example 3, except that the bent portion has an angular shape as shown in
an alkaline battery having the same construction as Example 4, except that the bent portion has an angular shape as shown in
The alkaline batteries of Comparative Examples 1 and 2 and Examples 1 through 8 were tested as follows.
100 batteries of each example were subjected to each of the following test procedures over a 1-to 4-month period. The number of batteries that showed leakage was counted at the end of each month.
1) Heat shock by alternately storing at 80° C. for 12 hours, then at −20° C. for 12 hours.
2) Stored at 80° C.
The batteries were subjected to each of the following test procedures. The discharge performance was rated relative to Comparative Example 1 (=100).
1) Discharge at 1000 mA by 10 spm/1 hpd (i.e., 1-hour discharge each day. Every 1 minute pulsed-discharge consisted of a 10 sec discharging at 1000 mA and a 50 sec off)
2) Continuous discharge at 1000 mA.
3) Continuous discharge at 100 mA.
20 sets of each example were subjected to each of the following test procedures. The number of exploded batteries was counted.
1) Single battery in series short-circuit test (Single battery was short-circuited at room temperature).
2) Four batteries in series short-circuit test (Four batteries connected in series were short-circuited at room temperature).
3) ¼ reverse connection short-circuit test (one of the four batteries connected in series was reversed and the batteries were short-circuited at room temperature).
The results of the leakage-proof performance test, the discharge performance test, and the safety test were shown for Comparative Examples 1 and 2 and Examples 1 through 8 in Table 1.
The results of Table 1 indicate that the discharge performance is increased by 10 to 25% in each of Comparative Example 2 and Examples 1 through 8 without reinforcing washer as compared to Comparative Example 1 with reinforcing washer. The leakage rating is favorable in each of Examples 1 through 8 with bent portion as compared to Comparative Example 2 without bent portion, or bent angle=0 degree. However, Examples 4 and 8, in which the difference between the two angles is excessively large, show unfavorable results in both the leakage rating and the safety rating. The improvement in the leakage rating is less significant when the difference between the two angles is relatively small as in Examples 1 and 5. In each of Examples 2, 3, 6 and 7, in which the difference between the two angles is in the range of 11 to 22 degrees, the results are as favorable as in Conventional Example with reinforcing washer both in the leakage rating and the safety rating. Examples 5 through 8, in particular Examples 5 and 8, in which the bent portion is formed into an angular shape, show significant improvement both in the leakage rating and the safety rating as compared to Examples 1 through 4, in particular Example 1 and 4, in which the bent portion has a radius of curvature (R) of 0.4 mm and is not formed as an angular shape.
In the above-describe alkaline battery of the present invention, the linking portion of the gasket includes an annular disc that is uniform in thickness and has a two-step profile with a bent portion formed at its middle portion as viewed along the radial direction. By deforming itself at its bent portion, the annular disc effectively absorbs the distortion and stress generated in the outer cylindrical portion on the sealing process of the battery. This keeps the thin portion from being exposed to significant stress. In this manner, the leakage-proof performance of the battery can be ensured and the operation pressure of the explosion-proof valve can be stabilized, ensuring the safety and leakage-proof performance of the battery. In addition, eliminating the reinforcing washer makes it possible to design a sealing with a decreased axial dimension. This improves the discharge performance of the battery.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-206920 | Jul 2005 | JP | national |
| 2006-056367 | Mar 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2006/309936 | 5/18/2006 | WO | 00 | 2/12/2009 |
